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101

Such leucogranitic material comprises nearly one-third of the rock
volume over areas of several acres around the small granodiorite stock
exposed on the north peak of the massif immediately northeast of Black-
pine Lake, and between this peak and the shoulder overlooking the lake.
About half occurs in definite dykes and sills; the remainder grades into
migmatites. No instance was noted of a continuously exposed body of
leucogranite grading into migmatite at one place and forming clean-cut
dykes and sills at another. However, the two types appear identical except
for their field occurrence. It seems reasonable to conclude that they are
of the same ultimate origin, and that in one case the granitic material
consolidated in situ, whereas in the other it became mobilized and travelled
along fractures and foliation planes before solidifying. Some dykes of
leucogranite cut across bodies of pegmatite and graphic granite; others are
cut by pegmatite.

Alaskite

Many dykes and irregular bodies in the gneisses and migmatites sur-
rounding the granodiorite stocks east of Blackpine Lake are composed of
cream-coloured, moderately coarse-grained alaskite. Typical specimens
contain 25 to 45 per cent quartz, 10 to 40 per cent potash feldspar, in about
equal proportions of microcline and what appears to be microperthite and
orthoclase, and the remainder albite-oligoclase feldspar, much of it un-
twinned. Some thin sections show no dark minerals except scattered grains
of magnetite; others contain a few flakes of biotite. Accessory minerals
include muscovite and sillimanite. The rock has an irregular texture, with
much intergrowth of the various minerals. Mortar structure, and strain
fractures in feldspar healed by quartz suggest that the alaskite consolidated
during a time of pronounced rock movement.

At least some of the alaskite dykes appear to be the youngest of all
the Wolverine complex rocks exposed, for they cut across pegmatite and
aplite dykes, and quartz veins.

Graphic Granite

Cream-coloured, coarse-grained, graphic granite occurs in irregular bodies
up to 100 feet in diameter among the gneiss-migmatite roof rocks above
the grey granodiorite exposed on the southwest shoulder of the massif north-
east of Blackpine Lake. The feldspar of this granite is in large, irregular
crystals, some of which are several inches long. The quartz is colourless,
arranged in characteristic cuneiform structures up to 4 inch long. The rock
contains about 70 per cent microperthite (?), 5 per cent twinned sodic
plagioclase, and 25 per cent quartz. The only accessory minerals noted
in thin section were fine, powdery, iron oxides. The graphic granite grades
into quartz-feldspar pegmatite.

Pegmatite

Small bodies of pegmatite are abundant above and around the stocks
of grey granodiorite northeast of Blackpine Lake. Swarms of dykes are
found at intervals along the ridges between these stocks and Chase
Mountain. Elsewhere they are very scarce, but appear in some abundance
on the crest of Butler Range, at the extreme east border of the map-area.